﻿// This file is part of YamlDotNet - A .NET library for YAML.
// Copyright (c) Antoine Aubry and contributors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
// of the Software, and to permit persons to whom the Software is furnished to do
// so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

using System;
using System.Collections.Generic;
using YamlDotNet.Core;

namespace YamlDotNet.RepresentationModel
{
    /// <summary>
    /// Represents an alias node in the YAML document.
    /// </summary>
    internal class YamlAliasNode : YamlNode
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="YamlAliasNode"/> class.
        /// </summary>
        /// <param name="anchor">The anchor.</param>
        internal YamlAliasNode(AnchorName anchor)
        {
            Anchor = anchor;
        }

        /// <summary>
        /// Resolves the aliases that could not be resolved when the node was created.
        /// </summary>
        /// <param name="state">The state of the document.</param>
        internal override void ResolveAliases(DocumentLoadingState state)
        {
            throw new NotSupportedException("Resolving an alias on an alias node does not make sense");
        }

        /// <summary>
        /// Saves the current node to the specified emitter.
        /// </summary>
        /// <param name="emitter">The emitter where the node is to be saved.</param>
        /// <param name="state">The state.</param>
        internal override void Emit(IEmitter emitter, EmitterState state)
        {
            throw new NotSupportedException("A YamlAliasNode is an implementation detail and should never be saved.");
        }

        /// <summary>
        /// Accepts the specified visitor by calling the appropriate Visit method on it.
        /// </summary>
        /// <param name="visitor">
        /// A <see cref="IYamlVisitor"/>.
        /// </param>
        public override void Accept(IYamlVisitor visitor)
        {
            throw new NotSupportedException("A YamlAliasNode is an implementation detail and should never be visited.");
        }

        /// <summary />
        public override bool Equals(object? obj)
        {
            return obj is YamlAliasNode other
                && Equals(other)
                && Equals(Anchor, other.Anchor);
        }

        /// <summary>
        /// Serves as a hash function for a particular type.
        /// </summary>
        /// <returns>
        /// A hash code for the current <see cref="T:System.Object"/>.
        /// </returns>
        public override int GetHashCode()
        {
            return base.GetHashCode();
        }

        /// <summary>
        /// Returns a <see cref="string"/> that represents this instance.
        /// </summary>
        /// <returns>
        /// A <see cref="string"/> that represents this instance.
        /// </returns>
        internal override string ToString(RecursionLevel level)
        {
            return "*" + Anchor;
        }

        /// <summary>
        /// Recursively enumerates all the nodes from the document, starting on the current node,
        /// and throwing <see cref="MaximumRecursionLevelReachedException"/>
        /// if <see cref="RecursionLevel.Maximum"/> is reached.
        /// </summary>
        internal override IEnumerable<YamlNode> SafeAllNodes(RecursionLevel level)
        {
            yield return this;
        }

        /// <summary>
        /// Gets the type of node.
        /// </summary>
        public override YamlNodeType NodeType
        {
            get { return YamlNodeType.Alias; }
        }
    }
}
